I will be presenting a seminar on Near-Field Terahertz Spectroscopy at the Metamaterials Laboratory (ITMO University, St. Petersburg) at 14:00 on the 17 of February.
Audio-recording of my talk 'Near-field terahertz spectroscopy: studying terahertz resonators on a micro-scale' presented at the Royal Society meeting: Particle, condensed matter and quantum physics: links via Max well's equations.
18-19 November 2015, Kavli Royal Society Centre, Chicheley Hall (UK)
(click to listen)
Detailed program and other recorded presentations at:
'Near-field terahertz spectroscopy: studying terahertz resonators on a micro-scale'
by I. Khromova
Terahertz radiation allows for non-destructive detection of objects and processes ’invisible’ at optical and microwave frequencies. Modern terahertz science promises break-through security, medical, and quality control techniques, as well as access to crucial astronomical observation and environmental monitoring. However, the emerging terahertz technology is held back by the scarcity of functional materials and devices required for manipulation of terahertz radiation.
This talk demonstrates opportunities and advantages of the near-field terahertz time-domain spectroscopy for direct studies of terahertz electromagnetic resonances occurring on a micrometre scale. As examples of micro-resonators, it considers conductive micro-fibres and dielectric micro-spheres. Micro-resonators are at the heart of numerous promising terahertz solutions, including the metamaterial approach – creating functional materials from artificial pre-designed resonant micrometre-sized ‘meta-atoms’. Experimental studies of micrometre-scale terahertz resonances are essential, yet inaccessible to common far-field spectroscopic techniques due to extreme sensitivity requirements.
This non-contact technique maps the field patterns of terahertz resonant modes excited in individual conductive or insulating micro-objects, and gives access to essential parameters of micro-resonators, including their resonance frequency, local field enhancement and quality factors. Depending on the underlying physics of observed terahertz resonances, it allows for material and structural characterisation of micro-objects.
This work uses the examples of carbon micro-fibres and titanium dioxide micro-spheres to show the advantages of near-field terahertz time-domain spectroscopy for non-contact terahertz conductivity probing and anisotropic material characterisation; and direct observation of versatile resonant modes, including surface-plasmon resonances in conductive dipoles, and magnetic dipole resonances in dielectric subwavelength terahertz resonators.
You are welcome to attend out invited talk titled 'Plasmonic resonances in carbon fibers observed with terahertz near-field microscopy' at 12pm on Monday, February 15,
Royal Society meeting: Particle, condensed matter and quantum physics: links via Maxwell's equations - 18-19 November 2015, London (UK)
Satellite meeting at Kavli Royal Society Centre, Chicheley Hall, Newport Pagnell, Buckinghamshire, MK16 9JJ
I will be presenting a talk titled 'Near-field terahertz spectroscopy: surface plasmons and Fano resonances at micro-scale'.
Please find the program, and registration details following the link
Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy
I. Khromova, M. Navarro-Navarro-Cía, I. Brener, J.L. Reno, A. Ponomarev, O. Mitrofanov,
Applied Physics Letters, 107, 021102 (2015)
We observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhancedelectric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1–5×10^4 S/m. This approach is suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.
Ultrasensitive terahertz/infrared waveguide modulators based on multilayer graphene metamaterial
Irina Khromova, Andrei Andryieuski and Andrei Lavrinenko
Laser & Photonics Reviews, Volume 8, Issue 6, pages 916–923, November 2014
This paper studies and classifies the electromagnetic regimes of multilayer graphene-dielectric artificial metamaterials in the terahertz/infrared range. The employment of such composites for waveguide-integrated modulators is analysed and three examples of novel tunable devices are presented. The first one is a modulator with excellent ON-state transmission and very high modulation depth: >38 dB at 70 meV graphene's electrochemical potential (Fermi energy) change. The second one is a modulator with extreme sensitivity towards graphene's Fermi energy - a minute 1 meV variation of the latter leads to >13.2 dB modulation depth. The third one is a tunable waveguide-based passband filter. The narrow-band cut-off conditions around the ON-state allow the latter to shift its central frequency by 1.25% per every meV graphene's Fermi energy change.
Dr. Irina Khromova